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Old 12-13-2012, 12:20 PM
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Gen I SBC Stamped rockers to roller rocker questions.

Hey, I build a stout 383 and put some 1.6 ratio stamped rockers on it (whoops) and one rocker arm split last night and left me on the road side. I'm planning on switching to a roller rocker with a machined body like this:

Proform Heavy-Duty Extruded Aluminum Roller Rocker Arms 66929 - SummitRacing.com

I am wondering what else I need to change besides the rocker arm to go to a roller rocker? Will they work with stock style rods and what not? Any other insight would be awesome. Oh I'm going to keep the same ratio too, 1.6.

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Old 12-13-2012, 02:44 PM
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Need to know what cyl heads and cam lift specs?
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Old 12-13-2012, 03:21 PM
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Quote:
Originally Posted by nskyline34 View Post
Hey, I build a stout 383 and put some 1.6 ratio stamped rockers on it (whoops) and one rocker arm split last night and left me on the road side. I'm planning on switching to a roller rocker with a machined body like this:

Proform Heavy-Duty Extruded Aluminum Roller Rocker Arms 66929 - SummitRacing.com

I am wondering what else I need to change besides the rocker arm to go to a roller rocker? Will they work with stock style rods and what not? Any other insight would be awesome. Oh I'm going to keep the same ratio too, 1.6.
What kind of cam where you running? It's VERY uncommon for stamped rockers to fail, especially under normal driving conditions. What pushrods, springs, and oil did you use? I'd look further into the cause of the failure before you just start spending money.
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Old 12-13-2012, 03:32 PM
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You need ARP (or equal) screw in rocker studs to use full roller rocker arms and poly-locks.
You should also use equal length Comp Cams High Tech .080" wall, 5/16" chromemoly push rods (or equal). The 1.6:1 rocker arms put more load on the push rods and rocker studs. Stock mild steel push rods usually fail.
The push rod slots or holes need to be elongated .070" towards the rocker stud boss. Taper the elongation .250" into the head. This will provide additional push rod to head clearance for the 1.6 rocker arms.

You can use a Comp Cams 4710 (Louis Tool) for the push rod guide hole enlargement or you can use a hand grinder and carefully grind the clearances without the tool. This requires that you remove the heads.
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Old 12-13-2012, 03:33 PM
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Quote:
Originally Posted by nskyline34 View Post
Hey, I build a stout 383 and put some 1.6 ratio stamped rockers on it (whoops) and one rocker arm split last night and left me on the road side. I'm planning on switching to a roller rocker with a machined body like this:

Proform Heavy-Duty Extruded Aluminum Roller Rocker Arms 66929 - SummitRacing.com

I am wondering what else I need to change besides the rocker arm to go to a roller rocker? Will they work with stock style rods and what not? Any other insight would be awesome. Oh I'm going to keep the same ratio too, 1.6.
Those are good ones alot of people use scorpion they make some good stuff.

What is the seat and max lift pressure? You may want to make sure the rockers can hold it. Where did you get them from. I would call the manufacturer and see if they are rated at that spring pressure. If so maybe have them walk you over the setup and make sure they are aligned right and get them to send a new rocker if it was just a weak one. If spring pressure was too much then make sure the new rockers will handle the load. Not all roller rockers are made the same.
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Old 12-14-2012, 01:33 AM
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The can isn't crazy, about .540" lift and the heads are world product sportsmans with 200cc runners and 64cc combustion chambers. How do pushrods affect this? I don't fully understand what you mean? And also how come for roller rockers I need threaded studs and not press in? Just trying to learn. Thanks so much for all the helpful tips!

It's in a mud bog / daily driven truck so it gets run pretty hard, so I'm thinking that this is just a weak one now. This setup isn't that hard on parts and nothing is that radical at all....right?

Keep 'me comin!
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Old 12-14-2012, 04:18 AM
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The 1.6 rocker arms have a higher lever ratio and places more load on the rocker studs and push rods. Compare the lever ratio to a see-saw with one seat closer to the pivot point than the other. It takes more force to push the shorter side down than the longer side. The higher ratio rockers also put more load on the timing chain but not enough extra load that would exceed the chains load bearing capacity unless it is a old chain with nylon sprocket teeth. The stock 3/8"-24 rocker stud will more likely pull out or break with 1.6 rocker arms due to the extra load, especially when used with high lift camshafts. . The tops of the stock 3/8" rocker studs are not perfectly flat in order to lock the poly-lock set screw. If you will notice, the factory never used 1.6 rocker arms on any engine that did not also have 7/16" rocker studs for those reasons.

The performance gains you will find with 1.6 rocker arms are minimal and are not worth the effort it takes to use 'em. The gain with the 1.6 rocker arms is the faster valve acceleration rate off the seat which gives about 3 degrees of additional valve duration. The faster valve action aids low RPM cylinder filling for a few more pounds of low end torque. You would never know the difference.
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Old 12-14-2012, 06:52 AM
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World Products Sportsman heads are already setup with screw in studs and guideplates so you're all set there.

Pushrod wise you want them to be as stiff as possible. Which means either a larger diameter or a thicker wall or both if you're turning high RPM's with a lot of valve spring pressure.

In your case unless you're looking at getting new guideplates then you need to stay with 5/16 diameter. Stock GM pushrods generally come in one of two styles. One piece swaged ends or ball ends that are welded on. If they're ball ended then I highly recommend upgrading. If you have swaged ends and your pushrod geometry is good then not upgrading to an after market push rod isn't going to mean you'll instantly have failures but it's good insurance against it.
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Old 12-14-2012, 08:58 AM
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Gen I SBC Stamped rockers to roller rocker questions.

If I was going to change over to full roller rockers I would stick with a well know name brand. Examples that I would choose are Harland Sharp, Lunati, Scorpion, Crane, etc. I would call Summit Racing with the cam specs, name brand of heads, like has been said order a set of Howards 5/16 heavy wall .080 pushrods, Howards Cams Swedged End Pushrods 95010 - SummitRacing.com.
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Old 12-14-2012, 09:02 AM
How fast is fast enough?
 
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Quote:
Originally Posted by nskyline34 View Post
The can isn't crazy, about .540" lift and the heads are world product sportsmans with 200cc runners and 64cc combustion chambers. How do pushrods affect this? I don't fully understand what you mean? And also how come for roller rockers I need threaded studs and not press in? Just trying to learn. Thanks so much for all the helpful tips!

It's in a mud bog / daily driven truck so it gets run pretty hard, so I'm thinking that this is just a weak one now. This setup isn't that hard on parts and nothing is that radical at all....right?

Keep 'me comin!
how much open pressure are you running? Did you check your pushrod length? You likely have a problem somewhere and throwing more rockers at it may not fix it.
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Old 12-14-2012, 10:54 AM
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You may be better off with a Comp pro magnum type rocker. They are rebuildable and are very durable since they are made of steel. Aluminum rockers may not hold up to the abuse from mud bogging etc. Crane, Scorpion and Harland Sharp also make good rockers.
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